Eve V. Clark
Stanford University

Different words mean different things. That is, wherever there is a difference in
form in a language, there is a difference in meaning. This is what, in 1980, I
called the Principle of Contrast. ¹ It is by virtue of this property that language
maintains its usefulness as a medium of communication. As Bolinger put it,
"any word which a language permits to survive must make its semantic contribu-
tion" ( 1977, p. ix). This applies as much to constructions as to words: "the same
holds for any construction that is physically distinct from any other construc-
tion" ( 1977, p. ix-x).

In the present paper I focus on the acquisition of meaning in light of the
Principle of Contrast. This principle makes specific predictions about acquisition
that are supported by data from many different domains. It shapes the lexicon for
immature and mature speakers alike. It also plays a role in establishing which
forms are conventional and thus contributes a solution to why children give up
over-regularizations in morphology and syntax. Finally, it helps account for
individual variation during acquisition.

I begin in the first section with a statement of the Principle of Contrast
together with its corollary, the Principle of Conventionality, and review its
predictions about language use in general. In the next section I review the
evidence for the Principle of Contrast in acquisition and show that children
observe it in both expected and unexpected ways from the earliest stages in the
acquisition of language. In the third section I look at the consequences of the
Principle of Contrast for the acquisition of morphology and of syntax, and the

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